While the advent of artificial fingernails was greeted with exceptional enthusiasm, complications since experienced have significantly dampened the enthusiasm. The most popular and widely-used artificial fingernail compositions have been two-part (liquid/powder) formulations wherein the liquid portion usually consists of methyl methacrylate monomer and a small amount of a polymerization accelerator or promoter, such as a tertiary amine, and the powder portion generally consists of polymethyl methacrylate and a catalyst, such as benzoyl peroxide.
In situ polymerization is effected by mixing a small amount of the liquid portion with a small amount of the powder portion on the end of a brush, and the mixture brushed on the nail surface to be repaired, protected or elongated. Elongation requires affixing a substrate means to the exposed edge of the nail, which means has the general contour of the natural nail and extends therefrom to the desired length and along the plane of the natural nail. The substrate is preferably of a material to which the polymerized mixture does not adhere. In this way it may be removed following construction of the artificial nail.
Blending the powder/liquid portions, as by brushing, results in at least a part of the powder dissolving in the liquid monomer, and the monomer polymerizes simultaneously through the action of the accelerator and catalyst. The mixing and brushing steps are repeated as often as needed to form the desired thickness and nail form. When polymerization is completed, the artificial nail may then be smoothed, shaped and a nail polish applied if desired.
As is well known, natural nails (fingernails and toenails) are afflicted with may problems related to health, accidents and abuse. For example, various genetic and disease-related abnormalities may disrupt nail growth, texture, thickness and strength, thus promoting fingertip injury and unsightliness. Accidents occur to produce nail damage, such as tearing, splitting, breaking and scarring. Likewise, nails are abused by so-called "nail-biters". There being no real medical solutions to these problems, the advent of artificial fingernails of the aforementioned type was a most welcome development.
Unfortunately, however, the fingernail preparations just described are not without serious inherent drawbacks and disadvantages. Important among these disadvantages is the fact that the principal constituent of the liquid portion, methyl methacrylate, is a low molecular weight, volatile compound with a penetrating, unpleasant odor. In fact, methyl methacrylate monomer has been shown to cause severe dermatological reactions, cardiovascular irregularities and other ailments. Although the prepolymerized powder appears safe in these formulations, the polymerization of monomer which proceeds in situ after mixing powder and liquid is far from complete, because of the nature of the reactant. Consequently, unreacted methyl methacrylate is available to cause dermatitis and other ailments.
Another disadvantage present formulations have is that the presence of unreacted low molecular weight methyl methacrylate in the matrix of the resulting polymer structure weakens same and generally leads not only to an artificial fingernail polymer of low mechanical strength, brittleness and lack of flexibility, but also leads to a lack of reproducibility of properties due to variations in the completeness of polymerization.
Another disadvantage of present formulations rests in the fact that they produce a high exotherm during polymerization, in some cases requiring that fingers be cooled in water following application.
A further disadvantage of present formulations is the time-consuming nature of the application process, which in part is a result of poor application qualities of the material, and in part a result of excessive time needed in finishing the nail because of the poor mechanical quality of the artificial nail.
It follows from the above-noted multiple disadvantages that there is a definite need for artificial nails which can be applied with greater safety and which exhibit greater strength, greater impact resistance, greater flexibility, greater processability, greater reproducibility, and lower exotherm during polymerization. The present invention not only fills this need but further provides even better wear resistance, retention, resistance to chemical solutions and moisture. In short, the compositions of instant discovery at once obviate the serious drawbacks hereinbefore discussed and provide superior physical, mechanical and cosmetic properties. As such, they are directed to the "cosmeticulous".
The following references, of varying degrees of relevance, were uncovered in a recent study of the artificial fingernail art:
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